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Flexible-fuel vehicles

A flexible-fuel vehicle or dual-fuel vehicle is an automobile that can typically alternate between two sources of fuel. A common example is a vehicle that can accept gasoline mixed with varying levels of ethanol (gasohol). Some cars carry a natural gas tank and one can switch from gasoline to gas.

Flexible-fuel vehicles in the United States

North American vehicles from approximately 1980 onward can run on 10% ethanol/90% gasoline (e.g., E10) with no modifications. Prior to 1980, many cars imported into the United States contained rubber, aluminium, and other materials that were generally non-compatible with any ethanol in their fuel delivery systems, and these cars experienced problems when E10 was first introduced.Cars made in the US from the late 1970's onward can run on E10 with no modifications. E10 fuel is widely available. Going beyond 10% ethanol generally requires special engineering.

In the United States, many flexible-fuel vehicles can accept up to 85% ethanol (E85). The fuel mixture is automatically detected by one or more sensors, and once detected, the ECU tunes the timing of spark plugs and fuel injectors so that the fuel will burn cleanly in the vehicle's internal combustion engine. Originally, sensors in both the fuel-line and in the exhaust system were used for flexible fuel vehicles. In recent years, manufacturers have instead opted to use only sensors in the exhaust manifold, before the catalytic converter, and to eliminate the fuel inline sensor. As E85 is more corrosive, special fuel lines are also required. Some manufacturers also required a different motor oil be used, but even this requirement is now dropped for all but one manufacturer.

In 1998, General Motors Corporation introduced their first light truck (an S10, with 2.2L engine) in a flexible-fuel configuration. In 1999, Ford Motor Company introduced a flexible-fuel option on its Ford Ranger pickup trucks, and it has also been an option on the company's Taurus model. Other manufacturers such as Mercedes-Benz, Chrysler/Dodge (namely certain models of Caravan) also are E85/Flexible fuel vehicles. Flexible fuel vehicles are often identified as such on the driver's side door, on the inside of the fuel fill access door, and by the VIN number.

As of 2005, most existing vehicles that are available to the public with flex-fuel engines are sport-utility vehicles or others in the "light truck" class. Sedans, wagons, and others are usually only available in flexible-fuel configurations as part of fleet vehicle purchases by companies. Starting in 2006, though, more widespread availability is planned for standard models intended for non-fleet sales.

A 1988 federal law provides an incentive for creating flexible fuel vehicles in the form of credits that can be used to relax Corporate Average Fuel Economy fuel efficiency standards. It is alleged that this efficiency relaxation has decreased overall US fleet efficiency, thereby resulting in increased nationwide fuel consumption.[1]

Over 4 million flexible-fuel vehicles are currently operated on the road in America, although a 2002 study found that less than 1% of fuel consumed by these vehicles is E85[2].

Flexible fuel vehicles as identified by the National Ethanol Vehicle Coalition.

Flexible-fuel vehicles in Brazil

Since the oil crisis in the 70's, Brazil has been selling ethanol as a fuel. Car manufacturers modified gasoline engines so as to better support alcohol characteristics (mainly changes in compression ratio and better robustness to protect from corrosion) and have been selling ethanol powered cars since then, in a lower scale than gas-powered cars. However, flexible fuel technology started to be investigated only in the 1990s. The flexible fuel car is built with an ethanol engine, a lambda probe to measure the mixture of gases that leaves the engine and a controller that regulates the input of fuel and the spark time, so as to correct the quality of the mixture. Those cars can run with arbitrary combinations of gasoline and alcohol (up to 100% of alcohol), but current engines cannot use pure gasoline - they are designed to run on gasoline mixed with 20% to 25% of ethanol, which is obligatory in Brazil.

In May 2003 Volkswagen built for the first time a production flexible fuel car, the Gol 1.6 Total Flex. Chevrolet followed two months later with the Corsa 1.8 Flexpower. The first compact car with flexible fuel engine was the Astra 2.0 Flexpower, and mid-size cars, minivans and pickup trucks followed later. As of 2005, popular manufacturers that build flexible fuel vehicles are Chevrolet, Fiat, Ford, Peugeot, Renault and Volkswagen. Flexible fuel cars were 22% of the car sells in 2004, 53% in 2005, and 75% and 90% rates are estimated for 2006 and 2007.

There's another type of flexible fuel vehicle that is not uncommon in Brazil. Those are the cars able to switch from gasoline to natural gas. The term "flex-fuel", however is never used to describe those cars; instead, they are called bi-fueled vehicles or tri-fueled if they are built with an ethanol-gasoline flexible fuel engine (and tetra-fueled if they can run on pure gasoline). These vehicles are always adapted in specialized houses after they are bought. In many cities, natural gas shares a small part of the fuel market with gasoline and ethanol. It has the advantage of being the cheaper fuel in the country and the disadvantage of having the lowest mileage and taking a lot of space in the trunk.

Trucks are diesel powered and there's no provision to convert them to flexible fuel vehicles. Instead the trend is to slowly replace diesel with bio-diesel. The currently allowed mixture is 98% diesel and 2% bio-diesel. The mixture of 95% diesel and 5% bio-diesel will become a requirement only in 2013.

Flexible-fuel vehicles in Europe

For a long time Ford Taurus was the only flexible-fuel vehicle sold in Sweden. It was later replaced by Ford Focus. In 2005 Saab begun selling its 9-5 Biopower, and Volvo its S40 and V50 with Flexifuel engines. There are also plans of selling E85 fuel, and then some flexible-fuel vehicles, in other European countries.

List of currently-produced flexible fuel vehicles

Europe

Ford Focus, Focus C-MAX
Saab 9-5
Volvo S40, V50

USA

Chrysler Sebring
Dodge Caravan, Durango, Grand Caravan, Ram Pickup, Stratus
Ford Crown Victoria, F-150, Grand Marquis, Taurus
Chevrolet Avalanche, Silverado, Suburban, Tahoe
GMC Sierra, Yukon
Nissan Titan

Brazil

Chevrolet: Celta, Classic, Corsa, Astra, Vectra, Montana, Meriva, Zafira
Citroën: C3
Fiat: Mille, Palio/Siena/Strada, Doblò, Idea, Stilo
Ford: Fiesta, EcoSport
Peugeot: 206
Renault: Clio, Mégane, Scénic
Volkswagen: Gol, Fox, Kombi

See also

• Plug-in hybrid electric vehicle
• Southern Grease - A great beginner's tutorial on using renewable fuel in diesel engines

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